Triangle
A triangle is a figure formed when three noncollinear points are connected by segments. Each pair of segments forms an angle of the triangle. The vertex of each angle is a vertex of the triangle.
The sum of the measures of the angles of a triangle is 180.
Area of a triangle
When you know the lenght of the base and the height, you can use the formula:
Area=·b·h, where b is the base and h is the height
Find the area of an acute triangle with a base of 15 inches and a height of 6 inches. 

Area=·b·h
Area=·(15 in)·(6 in)
Area=·90 in^{2}
Area=45 in^{2}
Area of a triangle (Heron's Formula)
Heron's formula gives the area in terms of the three sides of the triangle:
Suppose we know the values of the three sides
a, b and
c of the triangle.
If
s is the semiperimeter of the triangle, that is,
s = , then:
Find the area of triangle from a = 4, b = 6 and c = 4 using heron's formula. 

s = = = 7
= = 7.94